<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<iframe name="a" width="100px" height="100px" frameborder="1px"></iframe>
<iframe name="frame-2" width="200px" height="200px" frameborder="1px"></iframe>
<iframe name="frame-3" width="300px" height="300px" frameborder="1px"></iframe>

</body>
<script>
    /*window.parent;
    window.parent.frames;
    window.open('https://www.baidu.com', '_blank'); //_parent    _blank*/
    window.frames.frame
    window.frames[1].document.write('aaa');
    window.frames['frame-3'].location='https://www.baidu.com';
</script>
</html>